The leaflets and branches of the indigo plant yield an exquisite blue dye; people around the globe have used it to color textiles and clothing for centuries. Before the development of synthetic blue dyes, indigo was cultivated for this pigment rather than for medicinal use.
In the traditional medicine of India and China, indigo was used in the treatment of conditions we would now call epilepsy, bronchitis, liver disease, and psychiatric illness.1 However, there is no real scientific evidence for any of these uses.
Warning : Several species of indigo are poisonous. See Safety Issues for more information.
Based on its traditional use for liver problems, researchers have investigated whether indigo might protect the liver against chemically induced injury. Animal studies do suggest that extracts of the indigo species Indigofera tinctoria protect the liver from damage by toxic chemicals.2,3 No human trials, however, have been performed to examine indigo's effects on the liver.
The species Indigofera oblongifolia has been tested for its antibacterial and antifungal activity.4 In a test tube trial, this plant showed significant activity against certain types of bacteria and fungi. This research is still in its preliminary stages, so it is too early to tell whether Indigofera oblongifolia will prove useful for the treatment of any infectious diseases.
Note : A different plant called wild indigo ( Baptisia tinctoria), in combination with echinacea and white cedar, has been studied as a possible immune stimulant.5 However, wild indigo is not part of the Indigofera family of plants and is not discussed here.
No standard dosage of indigo has been established.
The indigo species Indigofera tinctoria has a history of use in traditional medical systems, and is regarded by herbalists as safe, other than the occasional allergic reactions that have been reported.6 However, comprehensive safety tests have not been performed. For this reason, indigo should not be used by pregnant or nursing women, young children, or individuals with severe liver or kidney disease. Safety in other individuals is unknown.
The species Indigofera spicata (formerly Indigofera endecaphylla ), however,is poisonous: it has killed cattle and other animals 7,8 and has caused birth defects in rats.9 Other indigo species have also been found to be lethal.10,11 For this reason, it is important to avoid ingesting indigo internally unless you are absolutely certain that it has been harvested and processed by expert, reliable individuals.
1. Anand KK, Chand D, Ghatak BJR. Protective effect of alcoholic extract of Indigofera tinctoria Linn. in experimental liver injury. Indian J Exp Biol. 1979;17:685–687.
2. Anand KK, Chand D, Ghatak BJR. Protective effect of alcoholic extract of Indigofera tinctoria Linn. in experimental liver injury. Indian J Exp Biol. 1979;17:685–687.
3. Anand KK, Chand D, Ghatak BJR. Histological evidence of protection by Indigofera tinctoria Linn. against carbontetrachloride induced hepatotoxicity—an experimental study. Indian J Exp Biol. 1981;19:298–300.
4. Dahot MU. Antibacterial and antifungal activity of small protein of Indigofera oblongifolia leaves. J Ethnopharmacol. 1999;64:277–282.
5. Wustenberg P, Henneicke-von Zepelin H-H, Kohler G, et al . Efficacy and mode of action of an immunomodulator herbal preparation containing Echinacea, wild indigo, and white cedar. Adv Ther. 1999;16:51–70.
6. Review of Natural Products. St. Louis, Mo: Facts and Comparisons; 1993: Indigo monograph.
7. Miller R, Smith CR. Seeds of Indigofera species: their content of amino acids that may be deleterious. J Agric Food Chem. 1973;21:909–912.
8. Finnegan RA, Mueller WH. Chemical examination of a toxic extract of Indigofera endecaphylla. The endecaphyllins. J Pharm Sci. 1965;54:1136–1144.
9. Pearn JH, Hegarty MP. Indospicine—the teratogenic factor from Indigoferaspicata extract causing cleft palate. Br J Exp Path. 1970;51:34–36.
10. Hegarty MP, Kelly WR, McEwan D, et al. Hepatotoxicity to dogs of horse meat contaminated with indospicine. Aust Vet J. 1988;65:337–340.
11. Miller R, Smith CR. Seeds of Indigofera species: their content of amino acids that may be deleterious. J Agric Food Chem. 1973;21:909–912.
Last reviewed December 2015 by EBSCO CAM Review Board Last Updated: 12/15/2015